The wide-spread use of antibiotics over the past decades to treat infectious diseases in humans, farm animals and aquaculture species has led to a gradual selection of bacterial strains which are resistant to such medication. The problem with microbial resistance to antibiotics is of special concern for the human health sector, which for decades have had these powerful compounds to control diseases and prevent spreading of pathogenic bacteria in the environment. This situation has fostered an intensive search for new antibiotics which differ from those used today in mode of action and hence which are not affectd by the resistance genes, selected as a result of previous and present use of antibiotics. The search for novel antibacterial principles has included also the marine environment and invertebrates living in this environment. In recent years, antimicrobial substances have been isolated from marine invertebrates. This includes several antibacterial polypeptides from horseshoe crab, short crab and molluscs. These polypeptides exhibit an antibacterial activity against various Gram-positive and Gram-negative bacteria. Glycoproteins with antibacterial activity have been isolated from sea hare and a bivalve mollusc. One well-known antibacterial protein is lysozyme. Lysozyme, however, exhibits an antibacterial activity against extremely limited Gram-positive bacteria such as Micrococcus. It is well known that proteins with lysozyme-like activity occur in many marine invertebrates including marine bivalves. Such proteins are believed to be involved in the host defense as well as being associated with digestive processes in marine bivalves. Bacteria are nutritive sources for filter feeders such as marine bivalves and a substance that is able to hydrolyse bacteria would fulfill the purpose of both defense and digestion. While it is known that an extract from the viscera of the Arctic scallop has been shown to have antibacterial effects on Aeromonas salmonicida and Vibrio salmonicida in vitro, it is considered that the tedious process for the production of such extracts coupled with the volume of such extracts required to be of commercial significance precluded the use of such extracts as a commercial candidate for use in the killing of fish pathogens. Accordingly, if the lysozyme antibacterial component of the viscera of Arctic scallop could be isolated and identified and the gene be isolated therefrom which would permit then the expression of the lysozyme antibacterial protein, there could then be provided to the art a significant system for the production of a novel antibacterial protein in amounts that would render such antibacterial protein a real candidate for the inhibitation and killing of bacterial pathogens.
It is thus an object of the present invention to provide a novel isolated and characterized antibacterial protein which is derived from the Islandic scallop--Chlamys islandica.
Another object of this invention is to provide a novel, isolated and characterized gene protein which will express a novel lysozyme protein having antibacterial activity.
A still further object of this invention is to provide a process for the expression of a novel gene derived from the Islandic scallop Chlamys islandica in a host microbial system.
Yet another object of this invention is to provide a novel construct for the expression of an antibacterial lysozyme protein.
Other aspects, objects and the several advantages of this invention will be apparent from the following disclosure and appended claims.